The present invention relates to a specialized scalpel. In particular, the scalpel is used in surgery to relieve pain in the carpal tunnel at the wrist.
People who perform repetitive motions or sustain vibratory stresses are susceptible to carpal tunnel syndrome. Carpal tunnel syndrome is caused by the compression of the nerves and tendons in the palm and wrist of the hands. Patients suffering from carpal tunnel syndrome report pain and numbness in the wrist, hand, and forearms, particularly at night. Treatments to relieve the pain of carpal tunnel syndrome include exercise, wrist splinting, steroid injection, rest, workplace alteration, anti-inflammatory agents, and correction of metabolic disorders. However, in some patients, surgical decompression of the carpal tunnel may be required to relieve the pain. To relieve the pain caused by carpal tunnel syndrome, the transverse carpal ligament that goes over the wrist, also known as the flexor retinaculum, just proximal to the palm, is transected. Prior to the transection of the transverse carpal ligament, a surgical incision is made into the palm of the hand, which causes a scar. The surgical incision on the palm may result in many potential complications, such as injuries, pain and swelling, and increased time for recovery.
Different surgical procedures and devices exist for carpal tunnel release surgery. Strickland, U.S. Pat. No. 5,387,222, discloses a carpal tunnel tome with a slender handle with a blade at one end for use in carpal tunnel release surgery. A pair of relatively blunt protuberances bounds the blade and prevents damage of surrounding tissues during the cutting procedure of the ligament. To access the ligament, a relatively short incision is made in the patient""s palm adjacent the distal edge of the transverse carpal ligament, also known as the flexor retinaculum. The incision and tissue are retracted to expose the distal portion of the transverse carpal ligament near the palm. The tome is advanced from the distal to proximal (i.e., palm to wrist), which allows visualization of the ligament. However, the distal to proximal incision is against the direction of the median nerve branching, so that there may be complications, such as laceration of the main trunk of the median nerve. In addition, the surgical procedure requires more than one instrument or a package consisting of retractors, elevators, and other surgical instruments.
A proximal to distal procedure, which avoids some of the disadvantages of Strickland""s distal to proximal procedure, is described in Pagnanelli et al., xe2x80x9cCarpal tunnel syndrome: surgical treatment using the Paine retinaculatomexe2x80x9d, J. Neurosurg 75: 77-81, July 1991. The surgery in Pagnanelli et al. is performed with a Paine retinaculatome, in which the knife edge of the retinaculatome extends from the flat portion of the knife in a perpendicular fashion. See id. at 78, FIG. 1. The knife has a concave leading edge with a hook and a blunt trailing edge. See id. at 78, FIG. 1, upper. The surgery begins with a small transverse incision in the distal wrist crease. See id. at 78. Tissue is spread and retracted to expose the underlying median nerve. See id. xe2x80x9cThe retinaculum is cut a few millimeters down into the palm and up the wrist to allow easy placement of the retinaculatome.xe2x80x9d See id. at 78-79. This easy placement is achieved by means of a hook on the Paine retinaculatome, which is latched onto the flexor retinaculum ligament, also known as the transverse carpal ligament. The base of the knife is positioned under the ligament and above the nerve, slightly slanted about 20xc2x0. See id. at 79. The leading edge of the knife cuts the carpal ligament as the retinaculatome is advanced into the palm. A very characteristic grating sound is produced by division of the ligament. See id.
The present invention concerns a specialized scalpel for relieving carpal tunnel syndrome. The specialized scalpel has an elongated member including a first portion for handling and a second portion. The second portion has a first surface, a second surface, and a blade on the first surface. The blade has a trailing edge and a sharp, convex leading edge. The leading edge rises gradually at a first angle with respect to the first surface so that when the leading edge is pushed against tissue to make an incision, damage to the surrounding tissue is reduced. The first angle is less than 90 degrees. In one embodiment, the specialized scalpel preferably has several features to reduce damage to the tissue, such as protective flanges, a flat bottom, and a curved front edge.
The specialized scalpel can be used in surgery to release the carpal tunnel in the hand. In carpal tunnel release surgery, a transverse incision is made in the patient""s distal wrist crease between the hand and the arm with a surgical instrument. The surgical instrument is positioned below the transverse carpal ligament and advanced in a closed procedure toward the patient""s fingertips until the transverse carpal ligament, also known as the flexor retinaculum, is completely transected. The surgical method can be performed with different surgical instruments. The specialized scalpel described above is particularly suited to the present surgical method, as it facilitates the surgical method with a curved front edge, a flat bottom, and a curved leading edge of the knife.
An advantage of the present invention is the prevention of damage by the use of the scalpel in surgery. The gentle slope of the leading edge facilitates ease of advancement of the blade in a closed, percutaneous resection within the carpal tunnel. The curved front edge displaces neurovascular structures and minimizes the likelihood of laceration. The flat bottom helps the knife glide over nerves and tendons and displace surrounding structures away from the blade.
Additionally, the proximal to distal procedure eliminates the need for an incision on the palm and results in a less conspicuous scar. Thus, pain and swelling are minimized, and recovery is expedited.
An additional advantage of the present invention is the use of the specialized scalpel in a partially closed, percutaneous procedure. The scalpel is introduced below the transverse carpal ligament after exposing the surrounding tissue and neurovascular structures. The tissue is not fully exposed by this procedure, and the risk of infection is thereby decreased. Complications of loss of function, pain, and scar tissue formation are also minimized. The partially closed, percutaneous procedure promotes faster healing.